This invention is directed to a device for evaporating volatile liquids, for example air fresheners and insecticides. The invention relates in particular to a device for evaporating volatile liquids from a container into a room, with the assistance of electrical power.
Devices are known, in which a bottle of volatile liquid has a wick projecting from it, and a heater is located in the vicinity of the distal end of the wick, to accelerate the evaporation of volatile liquid from the wick. The bottle, wick and heater are retained within a casing which carries an electric plug. To operate the heater the device is plugged into a wall socket.
Such devices are known, which purport to offer control of the rate of evaporation of the volatile liquids. In one device, described in Spanish patent application No. 9701388, the rate of evaporation is altered by varying the relative position of the wick and the heater (which typically is ring-shaped). In this patent application there is described a means for moving the container and the wick axially, through the action of a screw thread, while the ring heater is kept stationary.
In one device on the market, the relative movement of a ring heater and a wick is achieved by keeping the wick stationary and moving the heater axially.
In another device on the market, a tiltable barrel device is located at the distal end of the wick. This may be tilted about a horizontal axis to alter the air flow pathways at the distal end of the wick, and thereby alter the rate of evaporation.
However, we have found all such devices to be unsatisfactory in giving good adjustment. Indeed, in our tests we have sometimes found that the rate of evaporation of volatile liquids, when the device is in its minimum setting, to be higher than the rate of evaporation when the device is in its supposed maximum setting.
In accordance with a first aspect of the present invention, there is provided a device for evaporating a volatile liquid, the device comprising:
a container for the volatile liquid;
a wick which has a proximal end region within the container, with the proximal end thereof adjacent to the base of the container, and a distal end region above the container;
an electrical heater able to provide heat to the distal end region of the wick;
a casing which extends over the container and wick, and which has an aperture above the distal end of the wick; and
a tubular body in the region between the distal end of the wick and the casing, the tubular body being movable between highest and lowest positions to alter the rate of emission from the device of vapor evaporated from the wick;
wherein the vapor has a flow pathway from the wick to the exterior of the device through the tubular body, and wherein, when the tubular body is in its highest position, the vapor has an auxiliary flow pathway from the wick to the exterior of the device, which auxiliary flow pathway is not through the tubular body.
In accordance with a second aspect of the present invention, there is provided a tubular body forming part of a device for evaporating a volatile liquid, the device comprising:
a container for the volatile liquid;
a wick which has a proximal end region within the container, with the proximal end thereof adjacent to the base of the container, and a distal end region above the container;
an electrical heater able to provide heat to the distal end region of the wick; and
a casing which extends over the container and the wick, and which has an aperture above the distal end of the wick;
wherein the tubular body is located in the region between the distal end of the wick and the casing, the tubular body being movable between highest and lowest positions to alter the rate of emission from the device of vapor evaporated from the wick;
wherein the vapor has a flow pathway from the wick to the exterior of the device through the tubular body; and
wherein, when the tubular body is in its highest position, the vapor has an auxiliary flow path away from the wick to the exterior of the device, which auxiliary flow path is not through the tubular body.
In our tests of such devices we have found that the highest position of the tubular body is the position at which the evaporation rate is at a maximum. It is better, in this position, to provide such an auxiliary flow pathway than to require that all of the vapor escaping from the device into the exterior must pass through the tubular body.
However, it has been found that in certain conditions, such as when the tubular body is in its highest position, despite the auxiliary flow pathway, which increases the rate of evaporation of the volatile liquid, a portion of the liquid does not evaporate. This non-evaporated liquid escapes from the container, often running down internal surfaces of the container. This can become visible on certain external parts of the container. This is undesirable and unacceptable, as the escaping liquid is unsightly and may cause damage to areas near to the device.
Advantageously, the tubular body comprises an upper surface lying in a plane substantially at right angles to the axis of the tubular body. The surface comprises a wall extending around at least a part of the circumference of the upper surface and extending in a direction substantially perpendicular to the surface and away from the lower end of the tubular body.
The wall acts as a dam redirecting any non-evaporated liquid towards the heater in order that the liquid may be reheated. The presence of the wall thus ensures that any non-evaporated liquid is returned towards the heater where it is heated again. This process eliminates or at least significantly reduces the portion of volatile liquid which does not eventually evaporate during the heating process, and substantially eliminates liquid from becoming visible on certain external parts of the container.
Alternatively, or in addition, the tubular body contains one or more apertures formed in the upper surface. The one or more apertures allow liquid to escape towards the heater.
The surface may be substantially the same size and shape as the cross sectional area of the tubular body, but preferably, the upper surface has a greater radius than that of the cross sectional area of the tubular body.
Preferably, the upper surface is positioned co-axially with the tubular body. Because the upper surface of the tubular body is larger in area than the cross-sectional area of the tubular body, an upper surface is created. The upper surface extends horizontally beyond the tubular body and provides a greater catchment area for non-evaporated liquid, thus reducing further the portion of non-evaporated liquid which is able to escape from the device.
In one embodiment, the upper region of the casing may be provided with one or more separate openings, in addition to the aperture which is above the distal end of the wick. For example, there may be an array of openings around the aperture, so that the top of the casing has one aperture and further openings, preferably smaller openings, of xe2x80x9cpepper-potxe2x80x9d type.
In another embodiment, there may be a space between the upper end of the tubular body and the casing, in the highest position of the tubular body, through which space vapor may flow. Thus, the auxiliary flow pathway may be past the lower end of the tubular body, up the outside of the tubular body, over the upper end of the tubular body, through the space, and out through the aperture above the tubular body. Such embodiments have been shown to be very effective and are preferred embodiments of the present invention.
A further advantage of the wall-forming part of the upper surface of the tubular body, in a preferred embodiment of the invention, is that the wall prevents the upper end of the tubular body from making contact with the casing, thus ensuring that there is a space between the upper end of the tubular body and the casing in the highest position of the tubular body. This enhances evaporation of the volatile liquid.
The space between the upper end of the tubular body and the casing may be an annular space. Stops may be provided to prevent the tubular body reaching the casing in the highest position.
Alternatively, the device may be such that the tubular body contacts the casing in the highest position of the tubular body, with one or more openings being provided, in the upper region of the tubular body or in the part of the casing which contacts the tubular body. Such an opening is suitably of cut-out shape, by which we mean it extends to the end of the respective part.
In one embodiment, the upper end of the tubular body may suitably have one or more openings of cut-out shape. Thus, it may be of castellated form. Alternatively, a downwardly dependent skirt may project from said aperture, and the skirt may have one or more openings, suitably of cut-out shape. Thus, the skirt may be of castellated form, with the castellations facing in the downward direction.
Preferably, the aperture in the casing above the distal end of the wick is of substantially the same size and shape as the tubular body, in horizontal cross section.
Suitably, the ratio of the cross-sectional area of the space or opening, or the openings in total when there is more than one, to the transverse cross-sectional area of the flow pathway within the tubular body, is in a range of about 1:5 to about 5:1, preferably about 1:3 to about 3:2, more preferably about 1:2 to about 1:1, and especially about 6:10 to about 9:10. In devices in which the size of the space or of the opening(s) is at a minimum when the tubular body is in its highest position, these ratios refer to the situation when the tubular body is in its highest position.
There is a gap between the lower end of the tubular body and the heater, at least when the tubular body is in its highest position. Such a gap is preferably smaller in cross-sectional area than the horizontal cross-sectional area of the flow pathway within the tubular body. The ratio thereof may suitably be no more than about 1:2, preferably no more than about 1:5, most preferably no more than about 1:10. Such a gap is suitably smaller in area than the area of the opening, or of the openings in total when there is more than one. The ratio thereof may suitably be no more than about 1:2, preferably no more than about 1:5, most preferably no more than about 1:10.
Preferably, the heater and the wick are in fixed positions in the casing.
An important feature of this invention is that there be provided an auxiliary flow pathway when the tubular body is in its highest position. Such an auxiliary flow pathway is preferably also provided in all other positions of the tubular body, including in its lowest position.
A further important feature of this invention is that a means is provided for allowing non-evaporated volatile liquid to be redirected back towards the heater.
Suitably the heater is a ring heater, as is conventional, and the wick is aligned with the central axis of the ring heater. Preferably, the distal end region of the wick is within the hole defined by the ring heater. Suitably, the ring heater comprises an electrical resistor. Preferably, it is a thermistor. Preferably, it is powered by mains electricity, and the device is provided with plug formations to enable it to be operated from a mains electrical socket.
When a device is provided with plug formations and has the one or more openings in the upper end of the tubular body or in the lower end of a downwardly dependent skirt, preferably there is such an opening in the side of the tubular body or skirt facing toward the plug formations (i.e., the side nearest the plug formations). Preferably, there are two further openings centered on positions spaced about 90xc2x0 around the circumference from the center of the opening on the side which faces toward the plug formations. Preferably, there is also such an opening on the side facing away from the plug formations (i.e., farthest from the plug formations). Thus, in especially preferred embodiments there are at least four such openings.
Preferably, the tubular body does not overlie the distal end of the wick, even in the lowest position of the tubular body. Suitably, the tubular body is within a hole defined by the ring heater, even in its lowest position. Preferably, the lower end of the tubular body is substantially in the plane of the upper surface of the ring heater, when the tubular body in its highest position. Preferably, the lower end of the tubular body is above the distal end of the wick, even in the lowest position of the tubular body.